Caltech's Kate Hutton on the New Zealand Earthquake

In the wake of Monday's magnitude 6.3 earthquake in New Zealand—an aftershock of a 7.0 quake in September 2010—reporters looked to Caltech's experts for information and insight.

They got both from staff seismologist Kate Hutton, who spent Tuesday afternoon fielding questions from a steady stream of reporters and camera crews.

Despite being an aftershock—and thus having a lower magnitude than the original quake—Monday's temblor caused significantly more damage, and is currently responsible for 75 deaths, a number that's expected to rise over the next few days.

"The question is why there was so much more damage," Hutton said. The answer? In part, she said, it's because this was a shallow earthquake—occurring just 3.1 miles beneath the surface—and was centered much closer to the city of Christchurch than the original rupture.

Christchurch, which is New Zealand's second-largest city, lost much of its power, telecommunications, and water supplies.

In addition, Hutton noted, many of the buildings that were affected by the more-recent quake were likely damaged by the September temblor, but only now succumbed. In addition, most of those that crumbled, such as the 130-year-old Christchurch Cathedral, tended to be older, historical structures—the kind that seismologists tend to target for retrofitting.

"What this earthquake teaches us," she said, "is that it's possible to have large and damaging aftershocks late in the aftershock sequence." In fact, she added, the Christchurch aftershock was large enough that it will generate—and indeed has already generated—its own aftershocks, some with a magnitude as large as 5.5.

The lessons being learned in New Zealand right now are relevant to those of us in Southern California, she added, since these quakes were on a strike-slip fault similar to the San Andreas.

"New Zealand and Southern California have similar plate tectonics," said Hutton. "They're cousins, but not identical twins."